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Hindawi Publishing CorporationJournal of Skin CancerVolume 2011, Article ID 423239, 8 pagesdoi:10.1155/2011/423239

Review Article

BRAF in Melanoma: Pathogenesis, Diagnosis, Inhibition,and Resistance

Ryan J. Sullivan1 and Keith T. Flaherty2

1 Division of Hematology/Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02114, USA2 Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, MA 02114, USA

Correspondence should be addressed to Keith T. Flaherty, [email protected]

Received 10 July 2011; Revised 27 September 2011; Accepted 28 September 2011

Academic Editor: S. Ugurel

Copyright © 2011 R. J. Sullivan and K. T. Flaherty. This is an open access article distributed under the Creative CommonsAttribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work isproperly cited.

Since the initial discovery that a subset of patients with cutaneous melanoma harbor BRAF mutations, substantial research hasbeen focused on determining the pathologic consequences of BRAF mutations, optimizing diagnostic techniques to identify thesemutations, and developing therapeutic interventions to inhibit the function of this target in mutation-bearing tumors. Recently,advances have been made which are revolutionizing the standard of care for patients with BRAF mutant melanoma. This paperprovides an overview on the pathogenic ramifications of mutant BRAF signaling, the latest molecular testing methods to detectBRAF mutations, and the most recent clinical data of BRAF pathway inhibitors in patients with melanoma and BRAF mutations.Finally, emerging mechanisms of resistance to BRAF inhibitors and ways of overcoming this resistance are discussed.

1. Introduction

Melanoma is currently the 5th and 7th most common cancerin American men and women, respectively [1]. In addition,the incidence of melanoma has risen dramatically over thepast 60 years, increasing faster than all other solid tumors[2]. Although early-stage patients can be treated successfullywith surgical resection in the majority of patients, manywill develop disseminated disease. The prognosis for patientswith distant metastases from melanoma is dismal, and de-spite standard treatment, greater than 95% of patients withstage IV melanoma will die within five years and most pa-tients succumb within one year.

More recently, preclinical discoveries have led to signif-icant advances in the understanding of the key molecularsignaling events underlying the pathogenesis of melanoma.Most notably, a high percentage of tumors of melanocyticorigin have been shown to harbor activating mutations ofBRAF, which lead to its constitutive activity. Approximately70–80% of acquired melanocytic nevi and 40–60% of malig-nant melanoma contain a BRAF mutation, the vast majorityof which result in a single amino acid change at codon 600(BRAFV600E) [3, 4]. The resultant unopposed, constitutive

activation of extracellular signal-regulated kinase (ERK) leadsto the promotion of cellular growth and opposition of apop-tosis and, ultimately, transformation into melanoma [5].This enhanced signaling, however, also renders mutated cellssusceptible to the use of small molecule inhibitors whichtarget various BRAF pathway mediators [5–7].

2. RAF Signaling and Pathogenesis of Melanoma

The interaction between a growth factor receptor and itsligand typically induces a series of events, which promotecellular growth and survival. The RAS family members areGTPases which act as critical mediators in the transductionof such signals. Though RAS plays an important role in thehomeostasis of normal cell turnover, death, and survival,activating mutations in RAS family members (HRAS, KRAS,and NRAS) have been identified and associated with varioushuman malignancies [8]. In melanoma, NRAS mutationshave been identified in 10–25% of tumor samples andare thought to be an important driver of oncogenesis inthese patients [9–12]. Oncogenesis is mediated through theupregulation of several downstream signaling mechanisms,

2 Journal of Skin Cancer

most notably the mitogen-activated protein kinase (MAPK)and the phophatidy-inositol-3-kinase (PI3K) pathways [13].

Activated RAS triggers MAPK pathway activationthrough interactions with the RAF oncoproteins (BRAF andCRAF) leading to the initiation of a progrowth signalingcascade [14]. It is unclear whether it is BRAF or CRAF thattransmits signal from mutated NRAS to MEK, but the pre-ponderance of evidence suggests that CRAF is the primarymediator [15]. RAF interacts with MAPK/ERK kinase (MEK)thereby initiating MEK phosphorylation which in turn leadsto an activating phosphorylation of ERK [14]. The activationof ERK leads to a progrowth and transforming signal, whichappears to be critical to the pathogenesis of many malig-nancies. This pathway can be initiated by either RAF iso-form, BRAF, or CRAF, though CRAF also has pro-survivaleffects, in part through the upregulation of the anti-apop-totic proteins, nuclear factor kappa B (NF-κB), and B-cellleukemia 2 (BCL-2) [14]. Interestingly, unlike CRAF, acti-vated BRAF has no other known substrates. Thus, BRAFmutant melanomas signal exclusively through MEK andsubsequently ERK leading to oncogenesis. This characteristicrenders these tumors exquisitely sensitive to potent inhibitorsof the MAPK pathway.

3. Diagnostics/Detection

Since the identification of activating mutations of BRAFin melanoma, the technology for detection has improveddramatically. Standard mutational testing for BRAF in tumortissue typically utilizes techniques such as bidirectional directfluorescent sequencing and allele-specific polymerase chainreaction which are commercially available and offer highspecificity. The sensitivity of these assays, however, is limitedin that they are only able to detect the mutation if thetumor cells constitute >5–10% of the specimen submittedfor genetic analysis [16, 17]. While this degree of sensitivityis typically sufficient to detect the presence of the BRAFV600E

mutation in a homogenous tumor nodule, this is likely notsensitive enough to detect a few tumor cells in the back-ground of a high percentage of stromal or lymphatic ele-ments, infiltrating lymphocytes, or peripheral blood cells.

One concern regarding the utilization of mutation detec-tion techniques with enhanced sensitivity is that a positivetest might actually reflect the detection of a small subsetof mutant cells. While this might have interesting scientificconsequences, the clinical relevance of a tumor containing asmall amount of mutant BRAF cells is none, as these patientswould not be expected to benefit from BRAF inhibitors.This concern is warranted, as tumor heterogeneity has beendescribed in primary melanomas [18]. In addition, whileBRAF mutations are seen in the great majority of melano-cytic nevi, vertical growth phase melanomas, and metastaticmelanoma, they are rarely detected in radial growth phasemelanomas (10%), which is thought to be the initialmalignant lesion prior to a frankly invasive lesion [19]. Thissuggests that BRAF mutation may actually be an acquiredevent in early melanoma that leads to clonal expansion andtumor progression. Such polyclonality has not been seen in

individual metastatic tumors nor when tumors across mul-tiple sites from individual patients are sampled [18, 20]. Nev-ertheless, the application of enhanced sensitivity mutationalanalysis may not be just testing tumor samples but detectingsmall numbers of representative tumor cells in a backgroundof nonmalignant cells such as in lymph nodes and peripheralblood.

More advanced techniques and assays have been devel-oped which either provide increased sensitivity or obviatethe need for increased sensitivity. These next generation testsallow for more accurate testing on samples which containonly a small amount of tumor, as well as for the detectionmutations in various peripheral blood components (i.e.,lymphocytes, mononuclear cells, plasma, serum). The utilityof many of these tests have been explored in samples frommelanoma patients with varying results.

Amplification refractory mutation systems (ARMSs) area recently described, allele-specific technique which has en-hanced sensitivity (able to detect mutation sample contain-ing 1% mutant cells) compared to standard DNA sequenc-ing of formalin fixed paraffin-embedded (FFPE) tissues[21]. Another approach which greatly enhances sensitivityfor mutation detection is the utilization of assays whichselectively amplify mutant DNA/RNA in a sample. Usinga combination of allele-specific primers and locked nucleicacid primers, the detection of 10 melanoma cells in 1 mL ofblood has been described [22]. A third approach to increasethe sensitivity of mutation detection is reported to be ableto detect one mutant cell in a thousand nonmutant cells,taking advantage of a unique restriction enzyme site inthe wild-type alleles which allows for the digestion of thewild-type alleles and thus the enrichment of the mutantalleles [23]. Finally, the incorporation of COLD-PCR leadsto a near doubling of sensitivity in the detection of BRAFmutation from FFPE tissue when using standard sequencingand pyrosequencing [24].

In addition to new technologies (ARMS) and modifica-tions to routine techniques which lead to a greater sensitivityof mutation detection, the application of standard assayson previously untested samples is also changing how weapproach BRAF testing. BRAF analysis on free DNA in theserum and plasma has been reported as has the detectionof BRAF mutations from isolated, circulating tumor cells(CTCs) [25–30]. While CTC, serum and plasma BRAFanalysis appears possible, it is yet to be determined whetherthere will be routine clinical use for one or more of theseassays or if this will remain as only an experimental approach.

While the role of standard and experimental moleculardiagnostics is being utilized to identify specific mutationsof interest (i.e., BRAFV600E), both in tissue or blood, it alsomay be worthwhile to test for other mutations and anomaliesas these may indicate sensitivity to a particular treatment.For example, Sequenom MassARRAY technology is beingused to query larger panels of oncogenic mutations, usinga primer extension reaction followed by mass spectrometryto detect the products and identify mutations with potentialclinical consequences [31, 32]. Array comparative genomehybridization (aCGH) offers the opportunity to examine theentire genome for copy number changes, including both

Journal of Skin Cancer 3

amplifications and deletions that may confer sensitivity toa targeted therapy [33]. However, all these technologies areobviously limited in that they can only identify known,preselected anomalies. Whole genome analysis (WGA) hasthe potential to not only consolidate all or most of thesemodalities and tests to a single technology platform but alsoto identify additional genetic changes outside the design pa-rameters of these other assays [34]. WGA also offers the op-portunity to uncover previously unknown (perhaps patient-specific) mutations in melanoma genomes and to explorewhether particular profiles of mutations or polymorphismsmay be predictive of benefit from a particular therapy (i.e.,BRAF inhibitors, HD IL-2) [35]. Still, the clinical utility ofthese “Next Generation” tests in the care of patients withmelanoma is completely unknown.

4. Inhibitors of RAF Signaling (Less to MoreSpecific Mutant BRAF, CRAF, MEK, PerhapsMention ERK Inhibitors)

A series of small molecule inhibitors have been developedwhich target, with varying selectivity, wild-type BRAF,BRAFV600E, other mutant BRAF (at the 600 and 601 posi-tion), and CRAF. In addition, inhibitors of the downstreammediators of RAF activation, namely MEK and ERK, are alsobeing developed. In this section, only agents which have beentested clinically and reported publically are reviewed.

5. BRAF Inhibitors

5.1. Sorafenib. Sorafenib, a multitargeted tyrosine kinase in-hibitor of BRAF, CRAF, platelet-derived growth factor recep-tor (PDGFR), vascular endothelial growth factor receptor(VEGFR) 2, p38, and CKIT which was the first RAF-inhib-itor actively studied in patients with melanoma as it wasavailable for phase II testing in the same year in which BRAFmutations were first reported. Unfortunately, despite beingevaluated in numerous phase I, II, and III studies as a singleagent and in combination with chemotherapy, the clinicalutility of sorafenib has been disappointing. For example, ina single agent trial of sorafenib, the median progression-freesurvival for patients with melanoma was 11 weeks [36]. Sixpatients (16%) had stable disease at 6 months that persistedfor more than 12 months in some cases. However, only one ofthe 37 patients in the study had an actual response evaluationcriteria in solid tumor (RECIST-) defined tumor response.

This study was followed by several trials of sorafenib incombination with various cytotoxic agents, though the com-bination which was best studied was sorafenib, carboplatin,and paclitaxel [37–42]. Initial promise with this regimenwas described in a phase I trial of sorafenib in combinationwith carboplatin and paclitaxel in patients with solid tumors,where 24 patients with advanced melanoma were enrolled[39]. Ten patients with melanoma (42%) achieved anobjective response, and an additional 11 patients (46%) hadstable disease based on RECIST. The median progression-free survival was 43.7 weeks. These promising results led to aphase III trial comparing carboplatin/paclitaxel ± sorafenib

in patients with melanoma that had progressed followingtemozolomide or DTIC therapy. This trial (the PRISM study)enrolled 270 patients and showed no benefit for the additionof sorafenib to carboplatin/paclitaxel in this second-line pa-tient population [40]. The combination of carboplatin/pa-clitaxel and sorafenib was also compared to carboplatin/pa-clitaxel in a treatment naı̈ve population of patients withadvanced melanoma in a placebo-controlled randomizedphase III trial performed within the United States Intergroup(E2603). This trial enrolled 800 patients and found no benefitfor the addition of sorafenib on either median PFS or OS[41].

5.2. Higher Potency BRAF Inhibitors (PLX4032,GSK2118436).One major explanation proposed for the ineffectiveness ofsorafenib as a single agent in patients with melanoma is itsinability to completely inhibit BRAF, and in particular, BRAFcontaining the V600E mutation. Other inhibitors of BRAF,such as PLX-4032 and GSK2118436, have been developedand are more potent and selective inhibitors of mutant BRAFthan sorafenib [6, 7]. This enhanced inhibition of BRAFV600E

predictably has led to improved clinical activity of theseagents compared to sorafenib.

5.3. Vemurafenib. Vemurafenib was the first higher potencyBRAF inhibitor to complete phase I testing and show signif-icant clinical benefit [42]. In the phase I trial of PLX4032,11 of the 16 patients with tumors bearing the BRAFV600E

mutation who received a dose ≥240 mg twice daily in thedose escalation phase experienced tumor responses while noclinical responses were seen in the five patients with wild-type BRAF-containing tumor. In addition, 26 of 32 (81%)patients with the BRAFV600E mutant melanomas treated inan expansion cohort at the recommended phase II dose of960 mg twice daily had a clinical response, including twopatients achieving a complete response (CR). The estimatedmedian PFS was seven months which compares favorablyto previously available therapies for metastatic melanoma.Further, treatment with vemurafenib leads to a reduction inlevels of phosphorylated ERK (pERK) in tumors containingthe BRAFV600E mutation which is associated with clinicalresponse [43, 44]. Likely, this inhibition of pERK enhancesthe splicing of the proapoptotic BCL-2 family member BIMthereby promoting apoptosis of BRAFV600E cells [45].

These findings quickly led to the rapid accrual of botha single-agent phase II study (BRIM2) and a randomizedcontrolled phase III trial (BRIM3). The phase II trial enrolled132 patients with advanced melanoma who had received oneprior therapy. The objective response rate (ORR) was 53%with a CR rate of 5%, and the progression-free survival was6.7 months [46]. In the phase III trial, 675 patients withadvanced melanoma were randomized, to either the vemu-rafenib or dacarbazine as front-line therapy [47]. At the firstinterim analysis, treatment with vemurafenib was associatedwith a significant reduction in the risk of death and therisk of death (63% reduction) or disease progression (74%reduction), as well as a much higher ORR (48% versus 5%).These findings served as the basis for the FDA approval ofvemurafenib in August 2011.


5.4. GSK2118436. GSK2118436 is a second higher potencyBRAF inhibitor which has shown substantial clinical activity.In a phase I/II trial, similar to PLX4032, patients with theBRAFV600E mutation treated at the two highest dose levels(150 mg twice daily and 200 mg twice daily) had a high re-sponse rate (10/16 patients, 63%) [48]. In the eight pa-tients with non-BRAFV600E mutations (V600K, V600G, andK601E) treated at a dose of ≥100 mg twice daily, three hada partial response. Both of the patients with BRAFK601E

progressed after first restaging, suggesting that only patientswith BRAF mutations at the 600 position will respond totherapy.

6. MEK Inhibitors

Inhibitors of MEK, the downstream mediator of RAF acti-vation, and the only known substrate of BRAF have shownpromise in preclinical studies in melanoma and have begunto be investigated in the clinic with some encouraging results.MEK inhibitors may also be most useful in patients withBRAFV600E mutation; as mutational status correlates stronglywith response to MEK inhibition in murine melanomaxenograft models [49].

6.1. AZD6244. Two phase I trials of AZD6244 involving pa-tients with advanced solid tumors showed this agent to bewell tolerated and to possess some antitumor activity inpatients with melanoma [50, 51]. In the first trial, threeof eight with advanced melanoma patients treated withAZD6244 achieved a partial response; BRAF and NRASmutational status was unavailable [50]. While in the secondphase I study, only one response was seen in fourteen patientswith melanoma, though this subject had a documentedBRAF mutation and a complete response ongoing for overtwo years at the time of publication [51].

In addition, AZD6244 has shown promising results inmurine models, particularly in combination with chemo-therapy, setting the stage for combination trials [52]. Build-ing upon this, a pilot study of AZD6244 in combinationdacarbazine, docetaxel, or temsirolimus in patients withadvanced melanoma was performed [53]. Eighteen patientswere treated in whom BRAF and NRAS mutational statuswas known. Clinical response was seen in five out of ninepatients (55%) with a BRAF mutation, whereas no responseswere seen in any of the nine patients without a BRAF muta-tion which included four patients with an NRAS mutation.In addition, time to progression was significantly improvedin patients with a BRAF mutation compared to those patientswithout (median 31 weeks versus 8 weeks).

6.2. GSK1120212. GSK1120212 is a reversible, selective in-hibitor of MEK1/MEK2 which has been shown, in a phase Itrial, to have single-agent efficacy in patients with advanced,BRAFV600E mutant melanoma [54]. Specifically, eight of20 patients with BRAF mutant melanoma treated withGSK2110212 had a confirmed response with two patientsachieving a CR. Interestingly, two of 22 patients with wild-type BRAF had a PR with treatment, suggesting that some

melanoma tumors are dependent on ERK/MAP kinase sig-naling despite the absence of a BRAF mutation.

6.3. PD-0325901. A phase I trial of PD-0325901 enrolled 48patients with advanced melanoma, of whom 3 (6%) had aconfirmed PR, 10 (21%) had stable disease for ≥4 months,and a total of 15 (31%) patients showed reduction in Ki-67 tumor staining [55]. Mutational analysis data of thesepatients was not provided.

6.4. AS703026. Similar results have been recently reportedwith AS703026, which is a potent MEK1/2 inhibitor. In thephase I study, three of eight patients had a partial responsewith treatment in one of two treatment schedules [56]. Muta-tional status of the melanoma patients was not reported.

While the clinical data on MEK inhibitors is encouraging,it is quite preliminary. The true value of these agentsmust await phase II and phase III trials in patients withBRAF mutant melanoma. One such trial that is currentlyongoing is a randomized, phase III trial of GSK1220212compared with chemotherapy (either dacarbazine or pacli-taxel) in patients with melanoma harboring BRAF mutations(NCIT01245062).

7. Emerging Mechanisms of Resistance toBRAF Inhibition

Importantly, it appears that the great majority of patientstreated with single agent PLX-4032 will eventually exhibitdisease progression despite successful inhibition of theBRAFV600E and a high rate of objective response early in thecourse of therapy. Preliminary studies suggest that resistanceto PLX-4032 is not related to the development of a secondmutation which impairs the binding of the treatment drug toBRAF, a resistance mechanism noted for targeted therapy inother malignancies such as nonsmall cell lung cancer, chronicmyelogenous leukemia, and gastrointestinal stromal tumor[57–59]. Instead, resistance is mediated by reactivation of theMAPK pathway in most tumors through alternative means.

It is from in vitro studies of BRAFV600E-mutated cellswhich have been generated to exhibit acquired resistance toBRAF inhibitors, that has led to the first clues as to howBRAF-mutated cells are able to survive BRAF inhibition.It appears clear that reestablishment of MAPK signaling isthe key variable in acquired resistance to BRAF inhibition[60–63]. This can be achieved through upregulation ofreceptor tyrosine kinases (i.e., PDGFRB, ERBB2) [61, 62],activation of RAS [60, 62], upregulation of CRAF [61, 63],activation of the Ser/Thr MAPK kinases (COT) [61], anddevelopment of a secondary activating mutation in MEK[64, 65]. In addition, signaling through the PI3K pathwayinitiated by insulin growth factor receptor 1 (IGF-1R) isan alternative mechanism of acquired resistance which hasalso been described [66]. Of note, each of these mechanismshave been investigated and corroborated in small numbers oftumor samples from patients who had biopsies performed atthe time of resistance, and dependence on those upregulatedor mutated signaling mediators was not demonstrated.


Primary resistance to BRAF inhibition is seen in lessthan 10% of patients with BRAF mutant melanoma treatedwith vemurafenib [42]. While there is no data from clinicalsamples which helps to identify which patients are likelynot to benefit from BRAF inhibitors, preclinical studies sug-gest that elevated pretreatment levels of CRAF, as well as,baseline CCND1 amplification in tumors, leading to down-stream overexpression of Cyclin D1 and enhanced CDK4expression, are promising pretreatment biomarkers worthfurther investigation [63, 67].

In BRAF wild-type (BRAFWT) melanoma cells, the MAPKkinase pathway is activated by vemurafenib (and the anal-ogous PLX4720) leading to upregulation of MEK and ERKand enhanced proliferation [68, 69]. This appears to besecondary to the activation of CRAF with subsequent down-stream signaling through MEK and ERK with expected onco-genic consequences in BRAFWT cells [69]. Further, this CRAFactivation appears to be mediated through the formationof a heterodimer with the BRAFWT protein and/or CRAFhomodimer which is most apparent in RAS-mutated cells[70, 71]. In addition, PLX4720 enhances the levels of theantiapoptotic BCL-2 family member protein MCL-1 inNRAS mutant melanoma cells through enhanced signalingthrough the MAPK pathway [72]. While it is clear thatCRAF activation and enhanced MAPK pathway signalingoccur in BRAFWT melanoma cells (particularly those whichharbor an NRAS mutation) treated with BRAF inhibitorssuch as vemurafenib and PLX4720, the clinical relevance ofthis is uncertain. Specifically, it is not thought that clinicallyacquired resistance to vemurafenib, for example, occurssolely due to growth of a subset of BRAFWT melanoma cellsas persistence of the BRAFV600E mutation has been identifiedin all tumors analyzed and reported to date. In fact, it appearsthat specific changes in BRAFV600E-mutated cells allow foradaptations which lead to renewed growth despite continuedBRAF inhibition.

8. Future Directions

The establishment of single-agent efficacy of selective BRAFinhibitors, and to lesser extent MEK inhibitors, is a majorbreakthrough for the treatment of patients with BRAF muta-tion positive melanoma. Though most patients treated withthese agents are predicted to progress on treatment, theelucidation of the mechanisms of resistance described abovehelps guide future sequential and combinational therapy.Based on the finding that MAPK pathway activity is reac-tivated in melanoma following selective BRAF inhibition,the first combination trial of a selective BRAF inhibitor(GSK2118436) with a MEK inhibitor (GSK1120212) isunderway and appears tolerable with both agents being ad-ministered at their standard single-agent doses [73]. In ad-dition to this combination, trials with selective BRAF in-hibitors either in combination with or followed by IGF-R1 antagonists and other receptor tyrosine kinase inhibitorsmight be anticipated from the results of preclinical models ofresistance [61, 62, 66].

Another approach to enhancing the effectiveness of se-lective BRAF inhibitors and MEK inhibitors is the addition

of agents which might augment apoptosis. One such agentis ABT-263 which is a BH3-mimetic currently in clinicaldevelopment. In preclinical studies, the less bioavailablehomologous BH3-mimetic ABT-737 in combination witha MEK inhibitor led to enhanced lethality compared toeither agent alone [74]. Whether ABT-263 in combinationwith MEK or selective BRAF inhibitors will improve clinicaloutcomes is unknown, though it is perhaps worth exploringin an early-phase clinical trial.

In addition to combination therapy with molecularlytargeted agents which inhibit signaling induced by selectiveBRAF inhibition or promote apoptosis, another promisingapproach to maximizing the benefit of BRAF or MEK in-hibiters is to combine these agents with immunotherapy.Recently, immune checkpoint inhibitors, including the anti-CTLA-4 monoclonal antibody ipilimumab and the anti-PD monoclonal antibody MDX-1106, have shown singleagent efficacy in patients with metastatic melanoma [75, 76].Importantly, it appears that PLX4032 does not adverselyaffect human T-lymphocytes (T-cells) function while MEKinhibitors do [77]. Further, vemurafenib has been shown toimprove immune recognition by antigen-specific T cells inmelanoma [78]. These findings provide a rationale for astudy evaluating the safety and efficacy of selective BRAFinhibition in combination with immunotherapy, includingipilimumab, MDX1106, and possibly high-dose IL2.

9. Conclusions

It had been hoped for many years that the growing under-standing of the molecular pathways involved in melanomadevelopment and the increasing availability of specificinhibitors of these pathways would enable the rational de-velopment of future therapies. With the emergence of ve-murafenib and GSK2118436, the first molecularly targetedagents to lead to tumor responses in a large percentage ofpatients, a new approach to the treatment of melanoma hasbegun. As a result, all patients with advanced melanomashould have BRAF mutational analysis prior to commencingsystemic therapy. In those patients whose tumors harbor amutation in BRAF, every attempt should be made to treatthese patients with either of the two highly potent BRAFinhibitors. Additionally, as more is learned about the resis-tance mechanisms to BRAF inhibitors, the development ofcombination trials of novel molecularly targeted therapiescan be expected; further clinical improvements can only besorted out by carefully conducted preclinical and clinicalstudies that include pretreatment and on-treatment biopsies.With BRAF being established as the first point of vulnerabil-ity in melanoma, it is hoped that a molecular understandingof the limits of BRAF inhibition will lead to further clinicalbenefit.

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BRAFinMelanoma:Pathogenesis,Diagnosis,Inhibition ...downloads.hindawi.com/journals/jsc/2011/423239.pdf · Ampliﬁcation refractory mutation systems (ARMSs) are a recently described,